Differential drive circuits and single-ended drive circuits are commonly used in drive circuits for laser diodes. In a conventional single-ended drive circuit 150, as shown in FIG. 1, a modulated current is provided to the cathode of a laser diode (LD) 120 through resistor 125, which provides a damping resistance. The anode of the LD 120 is connected to a power supply (e.g., VCC) and a capacitor 115. Additionally, inductor 130 (comprising ferrite beads) isolates a bias output of the driver circuit 150 to provide the LD 120 with a bias. In the case of balanced DC and AC loads, the complementary output of the drive circuit 150 is increased to VCC by a parallel network consisting of inductor 105 and resistor 110. The resistor 110 matches the equivalent resistance of the LD 120 load and damping resistor 125. A RC parallel network (e.g., comprising resistor 135 and capacitor 140) provides high-frequency actuation and/or attenuation. The output capacitance of the driver circuit 150 (e.g., represented by capacitor 151 and capacitor 153) represents the equivalent capacitance of the transistors in drive circuit 150, the equivalent value of encapsulation, and the stray capacitance of a PCB on which the drive circuit 150 is mounted. The drive circuit 150 provides LD 120 with a modulated current (e.g., from current source 155) through a differential current switch circuit (e.g., comprising transistors 152 and 154), while a bias current generator (e.g., current source 157) provides LD 120 with a DC bias current via inductor 130.
In existing drive circuits (e.g., both single-ended and differential drive circuits), the output terminals (e.g., positive and negative) of the drive signal have the same transmission length and/or the same delay. That is, for example, the distance between the cathode/anode terminals of the LD and the cathode/anode terminals of the laser drive circuit is substantially the same for each of the terminals. For example, as shown in the timing diagram 200 of FIG. 2, the positive pulse 201 and the negative pulse 203 provided by the drive circuit 150 arrive at the load (i.e., LD 120) at the same time (e.g., at a time t1). The input waveform that the load experiences is DP−DN (i.e., waveform 201 minus waveform 203), shown as waveform 211. Waveform 211 arriving at the LD 120 has a single slope during the short rise time (e.g., from t1 to t2) and a single slope during the short fall time (e.g., from t3 to t4), resulting in high jitter and dispersion.